|It is important to
demonstrate different types of sisal fabrics and
carpets. The best carpet used in ASM operations is
the 3M Nomad Dirt Scraper Matting, especially the
type 6050 (medium traffic with backing) which
consists of a coiled vinyl structure; type 8100
(an un-backed version) can also be used. Nomad is
usually recommended for relatively coarse gold,
but can also trap fine gold efficiently. The price
of Nomad carpets in ASM sites can reach up to US$
150/m²; alternately, a Nomad type vinyl loop
carpet is available from manufacturers in China
for a fraction of this price. The Brazilian
company Sommer (subsidiary of the German company
Tarkett Sommer) sells 2 types of carpets widely
used by Brazilian ASM: "Multiouro
Tariscado" (which is good for gold of medium
sized rice grains) and "Multiouro Liso"
(which is good for - 0.15 mm gold). These carpets
can cost around US$ 10 to 15/m². None of these
carpets are easily accessible to ASM in Africa.
Sisal fabrics however, can cost as little as US$
3/m², and are available in most African
countries; depending on the type, they can be used
for coarse, medium and fine gold recovery. It is a
matter of trying different types. Raffia mats have
been used in Zimbabwe for fine gold concentration.
This definitely must be further investigated and
collaborative tests can be done with the miners to
establish the ideal type of sisal cloth.
mineral commonly found in gold-ore deposits, is
held by the magnetic sheeting, and forms a
fine-grained corduroy-like trapping mechanism on
the sluice floor. These inserts can be available
in any size, but they are relatively expensive.
For example, Cleangold® can manufacture a 60 x 50
cm insert for around US$ 165 (in USA). The main
advantage of this sluice is the high concentration
ratio. Gold becomes trapped in a magnetite layer
which can be easily scrapped and washed into a
pan. Using a magnet, the magnetite is removed and
a high grade of gold concentrate is obtained. In
many cases the use of mercury to amalgamate the
concentrate is not necessary. However, as the
magnetic separation isn’t always 100% efficient,
and the concentrate tailings can carry some gold,
so amalgamation or even leaching of the
concentrates is recommended. In one test comparing
the Cleangold® sluice with a centrifugal
concentrator, the sluice obtained slightly better
gold recoveries than the centrifuge. In a recent
field test in Venezuela conducted by UNIDO,
tailings from hammer mills and Cu-amalgamating
plates were passed without regrinding through a 60
cm long Cleangold® sluice box. About 11% of gold
in the tailings was recovered and the concentrate
analyzed 2850 ppm Au. The Cleangold sluice can
also take advantage of the fine pieces of steel
released from hammer and ball mills. They are also
concentrated on the magnetic sluice and play the
role of magnetite.
Africa) has devised interesting sluice boxes
(strakes) with rubber mat glued to it. Black
ribbed vinyl mats are also useful to recover gold;
they are easy to clean and cost in USA about US
pattern rubber riffle mat
moss sluice carpet
is the preferred matting for gold recovery. The moss traps
and holds gold inside loosely woven vinyl fibers which are
easily cleaned to recover the black sand concentrates and
your gold. Choose the thick type that is backed so the
gold cannot work through. This product can be purchased
online from a prospecting supply shop. If you are planning
to install several traps, this may be a bit expensive - if
so, you can use the cocoa-fiber mats and apply your own
backing as described below.
cocoa-fiber door mats
(These can be purchased fairly reasonably if you can catch
them on sale at your local hardware store - or research
and find a source to purchase this material by the square
yard.) These cocoa-fiber mats are commonly used as
entryway matting, because they do a great job of grabbing
and holding the dirt people track in on their shoes. As
such, it's perfect for catching and holding the heavies as
they flow down your sluice trap.
- The adhesive is used to seal the bottom of the
cocoa-fiber to prevent the black sand and gold from
working through the mat and escaping out of the bottom. I
think that the product “Liquid Nails” works very well.
Just spread it thickly on one side of the mat and allow to
dry. This can be found at any hardware store. There are
also spray-on products that are designed to prevent rugs
from sliding about - repeated spray applications of this
rubberized material will seal the back of your mat and
still remain fairly flexible.
or metal material to build a sluice box configuration.
Metal works best as wood tends to rot or warp when
submerged in water.